The present invention concerns a bushing device designed to be fitted through a hole in a wall, of the type having on the one hand a body and a cover each designed to be disposed on one side of the wall and on the other hand means for connecting the body and the cover to grip said wall between them, the body and the cover having aligned passages designed to receive a conductive rod.
The invention further concerns a bushing assembly of the type including a bushing device and a conductive rod which is received in the aligned passages of the body and the cover, passes completely through the body and the cover and has a connection for an electrical cable at one end.
Bushing devices designed to be fixed to a low-voltage output rod of a transformer are already known in themselves. A component of this kind has an electrical function consisting of feeding the output current of the transformer from the output windings inside the transformer casing to external electrical circuits with perfect electrical insulation between the conductive rod and the casing. To fulfill this electrical function in complete safety for many years, a bushing device must also be mechanically strong in order to withstand high operating temperatures (up to 250.degree. C.), vibration and static loads due to the mounting or to the assembly of the device.
Because of this, prior art bushing devices generally include a body made of ceramic or of a material hardened by heat of the epoxy resin type in the form of a skirt having an annular area passing through a hole formed in the wall of a transformer and an annular cover situated on the opposite side of the wall relative to the body, said body cooperating with the cover to grip the wall of the transformer to form a strong mechanical assembly which electrically insulates the conductive rod. The cohesion of the assembly is assured by fixing nuts screwed onto the ends of the output rod.
One such device is described in application EP-A-0.678.879 filed in the name of Applicant, for example.
Although they may fulfill their insulation function satisfactorily, the prior art devices are not highly resistant to external chemical and mechanical stresses.
The aim of the invention is to provide a solution to this problem by proposing a bushing device and a bushing assembly including it achieving satisfactory performance in terms of insulation and resistance to external chemical and mechanical attack.